Add basic support for reading floating-point values.

No guarantees are made as to the precision.

reader.c

@@ -3,6 +3,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <math.h>
 
 #include "gc.h"
 #include "builtin.h"
@@ -309,9 +310,114 @@ static value_t read_fixnum(reader_state_t *state, int radix)
 
 static value_t read_number(reader_state_t *state)
 {
-  value_t v = read_fixnum(state, 0);
+  bool negative = false;
+  fixnum_t num = 0;
+  native_float_t flt;
+  int radix;
+
+  if (state->ch == '-')
+  {
+    negative = true;
+    next_char(state);
+  }
+  else if (state->ch == '+')
+  {
+    next_char(state);
+  }
+
+  release_assert(isdigit(state->ch));
+
+  if (state->ch == '0')
+  {
+    next_char(state);
+
+    switch (state->ch)
+    {
+    case 'X':
+    case 'x':
+      next_char(state);
+      radix = 16;
+      break;
+    case 'B':
+    case 'b':
+      next_char(state);
+      radix = 2;
+      break;
+    case '0' ... '9':
+      ungetc(state->ch, state->file);
+      state->ch = '0';
+      radix = 8;
+      break;
+    default:
+      ungetc(state->ch, state->file);
+      state->ch = '0';
+      radix = 10;
+      break;
+    }
+
+    if (radix != 8)
+    {
+      /* Make sure we have at least one digit; if octal then the '0' counts instead */
+      release_assert(isalnum(state->ch));
+      release_assert(char_to_digit(state->ch) < radix);
+    }
+  }
+  else
+  {
+    radix = 10;
+  }
+
+  while (isalnum(state->ch))
+  {
+    fixnum_t digit = char_to_digit(state->ch);
+
+    if (digit >= radix)
+      break;
+
+    release_assert(num <= (FIXNUM_MAX/radix));
+
+    num *= radix;
+    num += digit;
+
+    next_char(state);
+  }
+
+  if (negative)
+    num = -num;
+
+  if ((radix != 10) || ((state->ch != '.') && (state->ch != 'E') && (state->ch != 'e')))
+  {
     release_assert(!issymbol(state->ch));
-  return v;
+    release_assert((FIXNUM_MIN <= num) && (num <= FIXNUM_MAX));
+    return fixnum_value(num);
+  }
+
+  /*
+   * Floating-point. No guarantees as to precision... really should use binary/hex.
+   */
+
+  flt = num;
+
+  if (state->ch == '.')
+  {
+    next_char(state);
+
+    for (native_float_t pv = negative ? -0.1 : 0.1; isdigit(state->ch); pv /= 10)
+    {
+      flt += (state->ch - '0') * pv;
+      next_char(state);
+    }
+  }
+
+  if ((state->ch == 'E') || (state->ch == 'e'))
+  {
+    next_char(state);
+    num = read_fixnum(state, 10);
+    flt *= pow(10, _get_fixnum(num));
+  }
+
+  release_assert(!issymbol(state->ch));
+  return make_float(flt);
 }
 
 static value_t read_string(reader_state_t *state)