feat(fstring): implement scientific and percentage formatting

examples/basic/23_format_spec.peb

@@ -1,33 +1,48 @@
-// Basic type
+print("Basic type")
 let a = 42
 print(f"int: {a:d}; hex: {a:x}; HEX: {a:X}; oct: {a:o}; bin: {a:b}")
+print()
 
-// Grouping
+print("Grouping")
 let b = 1234567890
 print(f"{b:,}")
 print(f"{b:_}")
+print()
 
 let c = 1234.5678
 print(f"{c:,._}")
 print(f"{c:_.,}")
+print()
 
-// Sign
+print("Sign")
 let d1 = 14
 let d2 = -26
 print(f"{d1} {d2}")
 print(f"{d1:+} {d2:+}")
 print(f"{d1:-} {d2:-}")
 print(f"{d1: } {d2: }")
+print()
 
-// Percentage
+print("Percentage")
 let pts = 19
 let total = 22
 print(f"Correct answers: {pts/total:.2%}")
+print()
 
-// Precision
+print("Precision")
 print(f"{c:8}")
 print(f"{c:8.2}")
 print(f"{c:.2}")
 print(f"{c:.8}")
+print()
 
-// Complex
+print("Scientific")
+print(f"{a:e}")
+print(f"{b:e}")
+print(f"{c:e}")
+print(f"{d1:e}")
+print(f"{d2:e}")
+print(f"{0:e}")
+print()
+
+print("Complex")

src/core/format_spec/string_formatter.py

@@ -1,3 +1,4 @@
+from math import log10, floor
 from typing import Any, Optional
 
 from src.core.format_spec.spec import FormatSpec
@@ -75,8 +76,12 @@ class StringFormatter:
                 res = obj
             case TokenType.T_BIN | TokenType.T_DEC | TokenType.T_HEX | TokenType.T_HEX_CAPS | TokenType.T_OCT:
                 res = self.format_int(obj, spec, fmt_type)
-            case TokenType.T_SCI | TokenType.T_FIX | TokenType.T_PCT:
+            case TokenType.T_FIX:
-                res = self.format_float(obj, spec, fmt_type)
+                res = self.format_float_fix(obj, spec, fmt_type)
+            case TokenType.T_PCT:
+                res = self.format_float_fix(obj * 100, spec, TokenType.T_FIX) + "%"
+            case TokenType.T_SCI:
+                res = self.format_float_sci(obj, spec, fmt_type)
 
         if spec.number.integral.width is not None:
             res = self.pad(res, spec.number.integral.width)
@@ -92,7 +97,7 @@ class StringFormatter:
 
         return sign + string
 
-    def format_float(self, value: float, spec: FormatSpec, fmt_type: TokenType) -> str:
+    def format_float_fix(self, value: float, spec: FormatSpec, fmt_type: TokenType) -> str:
         sign: str = self.make_sign(value, spec)
         value = abs(value)
         integer: int = int(value)
@@ -100,9 +105,16 @@ class StringFormatter:
         integer_spec = spec.number.integral
         decimal_spec = spec.number.decimal
 
+        precision: Optional[int] = None
+        if fmt_type == TokenType.T_SCI:
+            precision = 6
+
         if decimal_spec is not None:
             if decimal_spec.precision is not None:
-                decimal = round(decimal, decimal_spec.precision)
+                precision = decimal_spec.precision
+
+        if precision is not None:
+            decimal = round(decimal, precision)
 
         integer_str: str = self.format_int_part(integer, fmt_type, integer_spec.grouping)
         decimal_str: str = self.format_int_part(int(str(decimal)[2:]), fmt_type, None if decimal_spec is None else decimal_spec.grouping)
@@ -111,6 +123,14 @@ class StringFormatter:
 
         return f"{sign}{integer_str}{decimal_str}"
 
+    def format_float_sci(self, value: float, spec: FormatSpec, fmt_type: TokenType) -> str:
+        sign: str = self.make_sign(value, spec)
+        value = abs(value)
+        mag: int = 0 if value == 0 else floor(log10(value))
+        coef: float = value / (10 ** mag)
+        coef_str: str = self.format_float_fix(coef, spec, fmt_type)
+        return f"{sign}{coef_str}e{mag:+03d}"
+
     def format_int_part(self, value: int, fmt_type: TokenType, grouping: Optional[Token]):
         groups: int = 4
         string: str = str(value)