Merge pull request #3566 from Feoramund/fmt-refactor

Refactor `wprintf`

core/fmt/doc.odin

@@ -1,5 +1,5 @@
 /*
-package fmt implemented formatted I/O with procedures similar to C's printf and Python's format.
+package fmt implements formatted I/O with procedures similar to C's printf and Python's format.
 The format 'verbs' are derived from C's but simpler.
 
 Printing
@@ -33,6 +33,8 @@ Floating-point, complex numbers, and quaternions:
 	%E    scientific notation, e.g. -1.23456E+78
 	%f    decimal point but no exponent, e.g. 123.456
 	%F    synonym for %f
+	%g    synonym for %f with default maximum precision
+	%G    synonym for %g
 	%h    hexadecimal (lower-case) representation with 0h prefix (0h01234abcd)
 	%H    hexadecimal (upper-case) representation with 0H prefix (0h01234ABCD)
 	%m    number of bytes in the best unit of measurement, e.g. 123.45mib
@@ -61,9 +63,9 @@ For compound values, the elements are printed using these rules recursively; lai
 	bit sets           {key0 = elem0, key1 = elem1, ...}
 	pointer to above:  &{}, &[], &map[]
 
-Width is specified by an optional decimal number immediately preceding the verb.
+Width is specified by an optional decimal number immediately after the '%'.
 If not present, the width is whatever is necessary to represent the value.
-Precision is specified after the (optional) width followed by a period followed by a decimal number.
+Precision is specified after the (optional) width by a period followed by a decimal number.
 If no period is present, a default precision is used.
 A period with no following number specifies a precision of 0.
 
@@ -75,7 +77,7 @@ Examples:
 	%8.f   width 8, precision 0
 
 Width and precision are measured in units of Unicode code points (runes).
-n.b. C's printf uses units of bytes
+n.b. C's printf uses units of bytes.
 
 
 Other flags:
@@ -92,7 +94,7 @@ Other flags:
 	0      pad with leading zeros rather than spaces
 
 
-Flags are ignored by verbs that don't expect them
+Flags are ignored by verbs that don't expect them.
 
 
 For each printf-like procedure, there is a print function that takes no
@@ -105,19 +107,20 @@ Explicit argument indices:
 In printf-like procedures, the default behaviour is for each formatting verb to format successive
 arguments passed in the call. However, the notation [n] immediately before the verb indicates that
 the nth zero-index argument is to be formatted instead.
-The same notation before an '*' for a width or precision selecting the argument index holding the value.
+The same notation before an '*' for a width or precision specifier selects the argument index
-Python-like syntax with argument indices differs for the selecting the argument index: {N:v}
+holding the value.
+Python-like syntax with argument indices differs for selecting the argument index: {n:v}
 
 Examples:
-	fmt.printf("%[1]d %[0]d\n", 13, 37); // C-like syntax
+	fmt.printfln("%[1]d %[0]d", 13, 37) // C-like syntax
-	fmt.printf("{1:d} {0:d}\n", 13, 37); // Python-like syntax
+	fmt.printfln("{1:d} {0:d}", 13, 37) // Python-like syntax
 prints "37 13", whilst:
-	fmt.printf("%[2]*.[1]*[0]f\n",  17.0, 2, 6); // C-like syntax
+	fmt.printfln("%*[2].*[1][0]f", 17.0, 2, 6) // C-like syntax
-	fmt.printf("%{0:[2]*.[1]*f}\n", 17.0, 2, 6); // Python-like syntax
+	fmt.printfln("{0:*[2].*[1]f}", 17.0, 2, 6) // Python-like syntax
-equivalent to:
+is equivalent to:
-	fmt.printf("%6.2f\n",   17.0, 2, 6); // C-like syntax
+	fmt.printfln("%6.2f",   17.0) // C-like syntax
-	fmt.printf("{:6.2f}\n", 17.0, 2, 6); // Python-like syntax
+	fmt.printfln("{:6.2f}", 17.0) // Python-like syntax
-prints "17.00"
+and prints "17.00".
 
 Format errors:
 

core/fmt/fmt.odin

@@ -25,8 +25,6 @@ Info :: struct {
 	prec:      int,
 	indent:    int,
 
-	reordered:      bool,
-	good_arg_index: bool,
 	ignore_user_formatters: bool,
 	in_bad: bool,
 
@@ -527,13 +525,107 @@ wprintln :: proc(w: io.Writer, args: ..any, sep := " ", flush := true) -> int {
 // Returns: The number of bytes written
 //
 wprintf :: proc(w: io.Writer, fmt: string, args: ..any, flush := true, newline := false) -> int {
+	MAX_CHECKED_ARGS :: 64
+	assert(len(args) <= MAX_CHECKED_ARGS, "number of args > 64 is unsupported")
+
+	parse_options :: proc(fi: ^Info, fmt: string, index, end: int, unused_args: ^bit_set[0 ..< MAX_CHECKED_ARGS], args: ..any) -> int {
+		i := index
+
+		// Prefix
+		prefix_loop: for ; i < end; i += 1 {
+			switch fmt[i] {
+			case '+':
+				fi.plus = true
+			case '-':
+				fi.minus = true
+				fi.zero = false
+			case ' ':
+				fi.space = true
+			case '#':
+				fi.hash = true
+			case '0':
+				fi.zero = !fi.minus
+			case:
+				break prefix_loop
+			}
+		}
+
+		// Width
+		if i < end && fmt[i] == '*' {
+			i += 1
+			width_index, _, index_ok := _arg_number(fmt, &i, len(args))
+
+			if index_ok {
+				unused_args^ -= {width_index}
+
+				fi.width, _, fi.width_set = int_from_arg(args, width_index)
+				if !fi.width_set {
+					io.write_string(fi.writer, "%!(BAD WIDTH)", &fi.n)
+				}
+
+				if fi.width < 0 {
+					fi.width = -fi.width
+					fi.minus = true
+					fi.zero  = false
+				}
+			}
+		} else {
+			fi.width, i, fi.width_set = _parse_int(fmt, i)
+		}
+
+		// Precision
+		if i < end && fmt[i] == '.' {
+			i += 1
+			if i < end && fmt[i] == '*' {
+				i += 1
+				precision_index, _, index_ok := _arg_number(fmt, &i, len(args))
+
+				if index_ok {
+					unused_args^ -= {precision_index}
+					fi.prec, _, fi.prec_set = int_from_arg(args, precision_index)
+					if fi.prec < 0 {
+						fi.prec = 0
+						fi.prec_set = false
+					}
+					if !fi.prec_set {
+						io.write_string(fi.writer, "%!(BAD PRECISION)", &fi.n)
+					}
+				}
+			} else {
+				prev_i := i
+				fi.prec, i, fi.prec_set = _parse_int(fmt, i)
+				if i == prev_i {
+					fi.prec = 0
+					fi.prec_set = true
+				}
+			}
+		}
+
+		return i
+	}
+
+	error_check_arg :: proc(fi: ^Info, arg_parsed: bool, unused_args: bit_set[0 ..< MAX_CHECKED_ARGS]) -> (int, bool) {
+		if !arg_parsed {
+			for index in unused_args {
+				return index, true
+			}
+			io.write_string(fi.writer, "%!(MISSING ARGUMENT)", &fi.n)
+		} else {
+			io.write_string(fi.writer, "%!(BAD ARGUMENT NUMBER)", &fi.n)
+		}
+
+		return 0, false
+	}
+
 	fi: Info
-	arg_index: int = 0
 	end := len(fmt)
-	was_prev_index := false
+	unused_args: bit_set[0 ..< MAX_CHECKED_ARGS]
+	for i in 0 ..< len(args) {
+		unused_args += {i}
+	}
 
 	loop: for i := 0; i < end; /**/ {
-		fi = Info{writer = w, good_arg_index = true, reordered = fi.reordered, n = fi.n}
+		fi = Info{writer = w, n = fi.n}
 
 		prev_i := i
 		for i < end && !(fmt[i] == '%' || fmt[i] == '{' || fmt[i] == '}') {
@@ -567,191 +659,65 @@ wprintf :: proc(w: io.Writer, fmt: string, args: ..any, flush := true, newline :
 		}
 
 		if char == '%' {
-			prefix_loop: for ; i < end; i += 1 {
+			if i < end && fmt[i] == '%' {
-				switch fmt[i] {
+				io.write_byte(fi.writer, '%', &fi.n)
-				case '+':
-					fi.plus = true
-				case '-':
-					fi.minus = true
-					fi.zero = false
-				case ' ':
-					fi.space = true
-				case '#':
-					fi.hash = true
-				case '0':
-					fi.zero = !fi.minus
-				case:
-					break prefix_loop
-				}
-			}
-
-			arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
-
-			// Width
-			if i < end && fmt[i] == '*' {
 				i += 1
-				fi.width, arg_index, fi.width_set = int_from_arg(args, arg_index)
+				continue loop
-				if !fi.width_set {
-					io.write_string(w, "%!(BAD WIDTH)", &fi.n)
-				}
-
-				if fi.width < 0 {
-					fi.width = -fi.width
-					fi.minus = true
-					fi.zero  = false
-				}
-				was_prev_index = false
-			} else {
-				fi.width, i, fi.width_set = _parse_int(fmt, i)
-				if was_prev_index && fi.width_set { // %[6]2d
-					fi.good_arg_index = false
-				}
 			}
 
-			// Precision
+			i = parse_options(&fi, fmt, i, end, &unused_args, ..args)
-			if i < end && fmt[i] == '.' {
-				i += 1
-				if was_prev_index { // %[6].2d
-					fi.good_arg_index = false
-				}
-				if i < end && fmt[i] == '*' {
-					arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
-					i += 1
-					fi.prec, arg_index, fi.prec_set = int_from_arg(args, arg_index)
-					if fi.prec < 0 {
-						fi.prec = 0
-						fi.prec_set = false
-					}
-					if !fi.prec_set {
-						io.write_string(fi.writer, "%!(BAD PRECISION)", &fi.n)
-					}
-					was_prev_index = false
-				} else {
-					fi.prec, i, fi.prec_set = _parse_int(fmt, i)
-				}
-			}
 
-			if !was_prev_index {
+			arg_index, arg_parsed, index_ok := _arg_number(fmt, &i, len(args))
-				arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
+
+			if !index_ok {
+				arg_index, index_ok = error_check_arg(&fi, arg_parsed, unused_args)
 			}
 
 			if i >= end {
 				io.write_string(fi.writer, "%!(NO VERB)", &fi.n)
 				break loop
+			} else if fmt[i] == ' ' {
+				io.write_string(fi.writer, "%!(NO VERB)", &fi.n)
+				continue loop
 			}
 
 			verb, w := utf8.decode_rune_in_string(fmt[i:])
 			i += w
 
-			switch {
+			if index_ok {
-			case verb == '%':
+				unused_args -= {arg_index}
-				io.write_byte(fi.writer, '%', &fi.n)
-			case !fi.good_arg_index:
-				io.write_string(fi.writer, "%!(BAD ARGUMENT NUMBER)", &fi.n)
-			case arg_index >= len(args):
-				io.write_string(fi.writer, "%!(MISSING ARGUMENT)", &fi.n)
-			case:
 				fmt_arg(&fi, args[arg_index], verb)
-				arg_index += 1
 			}
 
 
 		} else if char == '{' {
+			arg_index: int
+			arg_parsed, index_ok: bool
+
 			if i < end && fmt[i] != '}' && fmt[i] != ':' {
-				new_arg_index, new_i, ok := _parse_int(fmt, i)
+				arg_index, i, arg_parsed = _parse_int(fmt, i)
-				if ok {
+				if arg_parsed {
-					fi.reordered = true
+					index_ok = 0 <= arg_index && arg_index < len(args)
-					was_prev_index = true
-					arg_index = new_arg_index
-					i = new_i
-				} else {
-					io.write_string(fi.writer, "%!(BAD ARGUMENT NUMBER ", &fi.n)
-					// Skip over the bad argument
-					start_index := i
-					for i < end && fmt[i] != '}' && fmt[i] != ':' {
-						i += 1
-					}
-					fmt_arg(&fi, fmt[start_index:i], 'v')
-					io.write_string(fi.writer, ")", &fi.n)
 				}
 			}
 
+			if !index_ok {
+				arg_index, index_ok = error_check_arg(&fi, arg_parsed, unused_args)
+			}
+
 			verb: rune = 'v'
 
 			if i < end && fmt[i] == ':' {
 				i += 1
-				prefix_loop_percent: for ; i < end; i += 1 {
+				i = parse_options(&fi, fmt, i, end, &unused_args, ..args)
-					switch fmt[i] {
-					case '+':
-						fi.plus = true
-					case '-':
-						fi.minus = true
-						fi.zero = false
-					case ' ':
-						fi.space = true
-					case '#':
-						fi.hash = true
-					case '0':
-						fi.zero = !fi.minus
-					case:
-						break prefix_loop_percent
-					}
-				}
-
-				arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
-
-				// Width
-				if i < end && fmt[i] == '*' {
-					i += 1
-					fi.width, arg_index, fi.width_set = int_from_arg(args, arg_index)
-					if !fi.width_set {
-						io.write_string(fi.writer, "%!(BAD WIDTH)", &fi.n)
-					}
-
-					if fi.width < 0 {
-						fi.width = -fi.width
-						fi.minus = true
-						fi.zero  = false
-					}
-					was_prev_index = false
-				} else {
-					fi.width, i, fi.width_set = _parse_int(fmt, i)
-					if was_prev_index && fi.width_set { // %[6]2d
-						fi.good_arg_index = false
-					}
-				}
-
-				// Precision
-				if i < end && fmt[i] == '.' {
-					i += 1
-					if was_prev_index { // %[6].2d
-						fi.good_arg_index = false
-					}
-					if i < end && fmt[i] == '*' {
-						arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
-						i += 1
-						fi.prec, arg_index, fi.prec_set = int_from_arg(args, arg_index)
-						if fi.prec < 0 {
-							fi.prec = 0
-							fi.prec_set = false
-						}
-						if !fi.prec_set {
-							io.write_string(fi.writer, "%!(BAD PRECISION)", &fi.n)
-						}
-						was_prev_index = false
-					} else {
-						fi.prec, i, fi.prec_set = _parse_int(fmt, i)
-					}
-				}
-
-				if !was_prev_index {
-					arg_index, i, was_prev_index = _arg_number(&fi, arg_index, fmt, i, len(args))
-				}
-
 
 				if i >= end {
 					io.write_string(fi.writer, "%!(NO VERB)", &fi.n)
 					break loop
+				} else if fmt[i] == '}' {
+					i += 1
+					io.write_string(fi.writer, "%!(NO VERB)", &fi.n)
+					continue
 				}
 
 				w: int = 1
@@ -770,31 +736,35 @@ wprintf :: proc(w: io.Writer, fmt: string, args: ..any, flush := true, newline :
 			switch {
 			case brace != '}':
 				io.write_string(fi.writer, "%!(MISSING CLOSE BRACE)", &fi.n)
-			case !fi.good_arg_index:
+			case index_ok:
-				io.write_string(fi.writer, "%!(BAD ARGUMENT NUMBER)", &fi.n)
-			case arg_index >= len(args):
-				io.write_string(fi.writer, "%!(MISSING ARGUMENT)", &fi.n)
-			case:
 				fmt_arg(&fi, args[arg_index], verb)
-				arg_index += 1
+				unused_args -= {arg_index}
 			}
 		}
 	}
 
-	if !fi.reordered && arg_index < len(args) {
+	if unused_args != {} {
-		io.write_string(fi.writer, "%!(EXTRA ", &fi.n)
+		// Use default options when formatting extra arguments.
-		for arg, index in args[arg_index:] {
+		extra_fi := Info { writer = fi.writer, n = fi.n }
-			if index > 0 {
+
-				io.write_string(fi.writer, ", ", &fi.n)
+		io.write_string(extra_fi.writer, "%!(EXTRA ", &extra_fi.n)
+		first_printed := false
+		for index in unused_args {
+			if first_printed {
+				io.write_string(extra_fi.writer, ", ", &extra_fi.n)
 			}
 
+			arg := args[index]
 			if arg == nil {
-				io.write_string(fi.writer, "<nil>", &fi.n)
+				io.write_string(extra_fi.writer, "<nil>", &extra_fi.n)
 			} else {
-				fmt_arg(&fi, args[index], 'v')
+				fmt_arg(&extra_fi, arg, 'v')
 			}
+			first_printed = true
 		}
-		io.write_string(fi.writer, ")", &fi.n)
+		io.write_byte(extra_fi.writer, ')', &extra_fi.n)
+
+		fi.n = extra_fi.n
 	}
 
 	if newline {
@@ -877,18 +847,16 @@ _parse_int :: proc(s: string, offset: int) -> (result: int, new_offset: int, ok:
 // Parses an argument number from a format string and determines if it's valid
 //
 // Inputs:
-// - fi: A pointer to an Info structure
-// - arg_index: The current argument index
 // - format: The format string to parse
-// - offset: The current position in the format string
+// - offset: A pointer to the current position in the format string
 // - arg_count: The total number of arguments
 //
 // Returns:
 // - index: The parsed argument index
-// - new_offset: The new position in the format string
+// - parsed: A boolean indicating if an argument number was parsed
-// - ok: A boolean indicating if the parsed argument number is valid
+// - ok: A boolean indicating if the parsed argument number is within arg_count
 //
-_arg_number :: proc(fi: ^Info, arg_index: int, format: string, offset, arg_count: int) -> (index, new_offset: int, ok: bool) {
+_arg_number :: proc(format: string, offset: ^int, arg_count: int) -> (index: int, parsed, ok: bool) {
 	parse_arg_number :: proc(format: string) -> (int, int, bool) {
 		if len(format) < 3 {
 			return 0, 1, false
@@ -896,30 +864,28 @@ _arg_number :: proc(fi: ^Info, arg_index: int, format: string, offset, arg_count
 
 		for i in 1..<len(format) {
 			if format[i] == ']' {
-				width, new_index, ok := _parse_int(format, 1)
+				value, new_index, ok := _parse_int(format, 1)
 				if !ok || new_index != i {
 					return 0, i+1, false
 				}
-				return width-1, i+1, true
+				return value, i+1, true
 			}
 		}
 
 		return 0, 1, false
 	}
 
+	i := offset^
 
-	if len(format) <= offset || format[offset] != '[' {
+	if len(format) <= i || format[i] != '[' {
-		return arg_index, offset, false
+		return 0, false, false
 	}
-	fi.reordered = true
 
 	width: int
-	index, width, ok = parse_arg_number(format[offset:])
+	index, width, parsed = parse_arg_number(format[i:])
-	if ok && 0 <= index && index < arg_count {
+	offset^ = i + width
-		return index, offset+width, true
+	ok = parsed && 0 <= index && index < arg_count
-	}
+	return
-	fi.good_arg_index = false
-	return arg_index, offset+width, false
 }
 // Retrieves an integer from a list of any type at the specified index
 //
@@ -2570,7 +2536,6 @@ fmt_value :: proc(fi: ^Info, v: any, verb: rune) {
 	if _user_formatters != nil && !fi.ignore_user_formatters {
 		formatter := _user_formatters[v.id]
 		if formatter != nil {
-			fi.ignore_user_formatters = false
 			if ok := formatter(fi, v, verb); !ok {
 				fi.ignore_user_formatters = true
 				fmt_bad_verb(fi, verb)

core/strconv/generic_float.odin

@@ -104,8 +104,7 @@ generic_ftoa :: proc(buf: []byte, val: f64, fmt: byte, precision, bit_size: int)
 	} else {
 		switch fmt {
 		case 'e', 'E':
-			prec += 1
+			decimal.round(d, prec + 1)
-			decimal.round(d, prec)
 		case 'f', 'F':
 			decimal.round(d, d.decimal_point+prec)
 		case 'g', 'G':

tests/core/fmt/test_core_fmt.odin

@@ -29,6 +29,8 @@ when ODIN_TEST {
 main :: proc() {
 	t := testing.T{}
 	test_fmt_memory(&t)
+	test_fmt_doc_examples(&t)
+	test_fmt_options(&t)
 
 	fmt.printf("%v/%v tests successful.\n", TEST_count - TEST_fail, TEST_count)
 	if TEST_fail > 0 {
@@ -36,12 +38,13 @@ main :: proc() {
 	}
 }
 
-test_fmt_memory :: proc(t: ^testing.T) {
+check :: proc(t: ^testing.T, exp: string, format: string, args: ..any, loc := #caller_location) {
-	check :: proc(t: ^testing.T, exp: string, format: string, args: ..any, loc := #caller_location) {
+	got := fmt.tprintf(format, ..args)
-		got := fmt.tprintf(format, ..args)
+	expect(t, got == exp, fmt.tprintf("(%q, %v): %q != %q", format, args, got, exp), loc)
-		expect(t, got == exp, fmt.tprintf("(%q, %v): %q != %q", format, args, got, exp), loc)
+}
-	}
 
+@(test)
+test_fmt_memory :: proc(t: ^testing.T) {
 	check(t, "5b",        "%m",    5)
 	check(t, "5B",        "%M",    5)
 	check(t, "-5B",       "%M",    -5)
@@ -52,8 +55,129 @@ test_fmt_memory :: proc(t: ^testing.T) {
 	check(t, "3.50 gib",  "%#m",   u32(mem.Gigabyte * 3.5))
 	check(t, "01tib",     "%5.0m", mem.Terabyte)
 	check(t, "-1tib",     "%5.0m", -mem.Terabyte)
-	check(t, "2.50 pib",  "%#5.m", uint(mem.Petabyte * 2.5))
+	check(t, "2 pib",     "%#5.m", uint(mem.Petabyte * 2.5))
 	check(t, "1.00 EiB",  "%#M",   mem.Exabyte)
 	check(t, "255 B",     "%#M",   u8(255))
 	check(t, "0b",        "%m",    u8(0))
 }
+
+@(test)
+test_fmt_doc_examples :: proc(t: ^testing.T) {
+	// C-like syntax
+	check(t, "37 13",  "%[1]d %[0]d",    13,   37)
+	check(t, "017.00", "%*[2].*[1][0]f", 17.0, 2, 6)
+	check(t, "017.00", "%6.2f",          17.0)
+
+	 // Python-like syntax
+	check(t, "37 13",  "{1:d} {0:d}",    13,   37)
+	check(t, "017.00", "{0:*[2].*[1]f}", 17.0, 2, 6)
+	check(t, "017.00", "{:6.2f}",        17.0)
+}
+
+@(test)
+test_fmt_options :: proc(t: ^testing.T) {
+	// Escaping
+	check(t, "% { } 0 { } } {", "%% {{ }} {} {{ }} }} {{", 0 )
+
+	// Prefixes
+	check(t, "+3.000", "%+f",   3.0 )
+	check(t, "0003",   "%04i",  3 )
+	check(t, "3   ",   "% -4i", 3 )
+	check(t, "+3",     "%+i",   3 )
+	check(t, "0b11",   "%#b",   3 )
+	check(t, "0xA",    "%#X",   10 )
+
+	// Specific index formatting
+	check(t, "1 2 3", "%i %i %i",          1, 2, 3)
+	check(t, "1 2 3", "%[0]i %[1]i %[2]i", 1, 2, 3)
+	check(t, "3 2 1", "%[2]i %[1]i %[0]i", 1, 2, 3)
+	check(t, "3 1 2", "%[2]i %i %i",       1, 2, 3)
+	check(t, "1 2 3", "%i %[1]i %i",       1, 2, 3)
+	check(t, "1 3 2", "%i %[2]i %i",       1, 2, 3)
+	check(t, "1 1 1", "%[0]i %[0]i %[0]i", 1)
+
+	// Width
+	check(t, "3.140",  "%f",  3.14)
+	check(t, "3.140",  "%4f", 3.14)
+	check(t, "3.140",  "%5f", 3.14)
+	check(t, "03.140", "%6f", 3.14)
+
+	// Precision
+	check(t, "3",       "%.f",  3.14)
+	check(t, "3",       "%.0f", 3.14)
+	check(t, "3.1",     "%.1f", 3.14)
+	check(t, "3.140",   "%.3f", 3.14)
+	check(t, "3.14000", "%.5f", 3.14)
+
+	check(t, "3.1415",  "%g",   3.1415)
+
+	// Scientific notation
+	check(t, "3.000000e+00", "%e",   3.0)
+
+	check(t, "3e+02",        "%.e",  300.0)
+	check(t, "3e+02",        "%.0e", 300.0)
+	check(t, "3.0e+02",      "%.1e", 300.0)
+	check(t, "3.00e+02",     "%.2e", 300.0)
+	check(t, "3.000e+02",    "%.3e", 300.0)
+
+	check(t, "3e+01",        "%.e",  30.56)
+	check(t, "3e+01",        "%.0e", 30.56)
+	check(t, "3.1e+01",      "%.1e", 30.56)
+	check(t, "3.06e+01",     "%.2e", 30.56)
+	check(t, "3.056e+01",    "%.3e", 30.56)
+
+	// Width and precision
+	check(t, "3.140", "%5.3f",          3.14)
+	check(t, "3.140", "%*[1].3f",       3.14, 5)
+	check(t, "3.140", "%*[1].*[2]f",    3.14, 5, 3)
+	check(t, "3.140", "%*[1].*[2][0]f", 3.14, 5, 3)
+	check(t, "3.140", "%*[2].*[1]f",    3.14, 3, 5)
+	check(t, "3.140", "%5.*[1]f",       3.14, 3)
+
+	// Error checking
+	check(t, "%!(MISSING ARGUMENT)%!(NO VERB)", "%" )
+
+	check(t, "1%!(EXTRA 2, 3)", "%i",    1, 2, 3)
+	check(t, "2%!(EXTRA 1, 3)", "%[1]i", 1, 2, 3)
+
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(EXTRA 0)", "%[1]i", 0)
+
+	check(t, "%!(MISSING ARGUMENT)",               "%f")
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(NO VERB)", "%[0]")
+	check(t, "%!(BAD ARGUMENT NUMBER)",            "%[0]f")
+
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(NO VERB) %!(MISSING ARGUMENT)", "%[0] %i")
+
+	check(t, "%!(NO VERB) 1%!(EXTRA 2)", "%[0] %i", 1, 2)
+
+	check(t, "1 2 %!(MISSING ARGUMENT)",    "%i %i %i",    1, 2)
+	check(t, "1 2 %!(BAD ARGUMENT NUMBER)", "%i %i %[2]i", 1, 2)
+
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(NO VERB)%!(EXTRA 0)", "%[1]", 0)
+
+	check(t, "3.1%!(EXTRA 3.14)", "%.1f", 3.14, 3.14)
+
+	// Python-like syntax
+	check(t, "1 2 3", "{} {} {}",          1, 2, 3)
+	check(t, "3 2 1", "{2} {1} {0}",       1, 2, 3)
+	check(t, "1 2 3", "{:i} {:i} {:i}",    1, 2, 3)
+	check(t, "1 2 3", "{0:i} {1:i} {2:i}", 1, 2, 3)
+	check(t, "3 2 1", "{2:i} {1:i} {0:i}", 1, 2, 3)
+	check(t, "3 1 2", "{2:i} {0:i} {1:i}", 1, 2, 3)
+	check(t, "1 2 3", "{:i} {1:i} {:i}",   1, 2, 3)
+	check(t, "1 3 2", "{:i} {2:i} {:i}",   1, 2, 3)
+	check(t, "1 1 1", "{0:i} {0:i} {0:i}", 1)
+
+	check(t, "1 1%!(EXTRA 2)", "{} {0}", 1, 2)
+	check(t, "2 1", "{1} {}", 1, 2)
+	check(t, "%!(BAD ARGUMENT NUMBER) 1%!(EXTRA 2)", "{2} {}", 1, 2)
+
+	check(t, "%!(BAD ARGUMENT NUMBER)",                       "{1}")
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(NO VERB)",            "{1:}")
+	check(t, "%!(BAD ARGUMENT NUMBER)%!(NO VERB)%!(EXTRA 0)", "{1:}", 0)
+
+	check(t, "%!(MISSING ARGUMENT)",                        "{}" )
+	check(t, "%!(MISSING ARGUMENT)%!(MISSING CLOSE BRACE)", "{" )
+	check(t, "%!(MISSING CLOSE BRACE)%!(EXTRA 1)",          "{",  1)
+	check(t, "%!(MISSING CLOSE BRACE)%!(EXTRA 1)",          "{0", 1 )
+}