Fix fuel implementation in PHP

ext/php/run.php

@@ -87,7 +87,7 @@ function cmdRun(string $bundlePath, array $args): void
     debugTime('built expression');
 
     fwrite(STDERR, "Reducing kernel application...\n");
-    $result = reduce($expr, 1_000_000);
+    $result = reduce($expr, 1_000_000_000);
     debugTime('reduced kernel application');
 
     [$kind, $value, $rest] = unwrapResult($result);

ext/php/src/functions.php

@@ -21,6 +21,14 @@ $GLOBALS['ARB_B']   = [0 => 0];
 $GLOBALS['ARB_NEXT'] = 1;
 $GLOBALS['ARB_CONS_CACHE'] = [];
 
+function spendFuel(int &$fuel): void
+{
+    if ($fuel <= 0) {
+        throw new \RuntimeException('fuel exhausted');
+    }
+    $fuel--;
+}
+
 function newNode(int $tag, int $a, int $b = 0): int
 {
     $id = $GLOBALS['ARB_NEXT']++;
@@ -100,12 +108,12 @@ function newAppFast(int $f, int $x, array &$TAG, array &$A, array &$B): int
     return $id;
 }
 
-function apply_(int $a, int $b, int $fuel = 1_000_000): int
+function apply_(int $a, int $b, int $fuel = 100_000_000_000_000_000): int
 {
     return reduce(app($a, $b), $fuel);
 }
 
-function reduce(int $term, int $fuel = 1_000_000): int
+function reduce(int $term, int $fuel = 100_000_000_000_000_000): int
 {
     return whnf($term, $fuel);
 }
@@ -167,6 +175,7 @@ function whnf(int $term, int &$fuel): int
         if ($left === 0) {
             $term = $right;
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -178,6 +187,7 @@ function whnf(int $term, int &$fuel): int
                 $TAG, $A, $B
             );
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -195,6 +205,7 @@ function whnf(int $term, int &$fuel): int
         if ($arg === 0) {
             $term = $A[$left];
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -202,6 +213,7 @@ function whnf(int $term, int &$fuel): int
         if ($atag === 1) {
             $term = newAppFast($B[$left], $A[$arg], $TAG, $A, $B);
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -213,6 +225,7 @@ function whnf(int $term, int &$fuel): int
                 $TAG, $A, $B
             );
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }