add -Wdouble-promotion warning and fix issues it brings up

examples/core/makefile

@@ -23,7 +23,7 @@ DEPS=$(SQUIGGLE) $(MATH)
 
 ## Flags
 DEBUG= #'-g'
-WARN=-Wall -Wextra 
+WARN=-Wall -Wextra -Wdouble-promotion
 STANDARD=-std=c99
 OPTIMIZED=-O3  #-Ofast
 

examples/more/makefile

@@ -25,7 +25,7 @@ DEPS=$(SQUIGGLE) $(SQUIGGLE_MORE) $(MATH) $(OPENMP)
 
 ## Flags
 DEBUG= #'-g'
-WARN=-Wall -Wextra 
+WARN=-Wall -Wextra -Wdouble-promotion
 STANDARD=-std=c99
 WARNINGS=-Wall
 OPTIMIZED=-O3  #-Ofast

squiggle.c

@@ -50,7 +50,7 @@ double sample_unit_normal(uint64_t* seed)
     // // See: <https://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform>
     double u1 = sample_unit_uniform(seed);
     double u2 = sample_unit_uniform(seed);
-    double z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
+    double z = sqrt(-2.0 * log(u1)) * sin(2 * PI * u2);
     return z;
 }
 

squiggle_more.c

@@ -248,8 +248,9 @@ box inverse_cdf_double(double cdf(double), double p)
 
     // 1. Make sure that cdf(low) < p < cdf(high)
     int interval_found = 0;
-    while ((!interval_found) && (low > -FLT_MAX / 4) && (high < FLT_MAX / 4)) {
+    while ((!interval_found) && (low > -DBL_MAX / 4) && (high < DBL_MAX / 4)) {
-        // ^ Using FLT_MIN and FLT_MAX is overkill
+        // for floats, use FLT_MAX instead
+        // Note that this approach is overkill
         // but it's also the *correct* thing to do.
 
         int low_condition = (cdf(low) < p);
@@ -314,8 +315,9 @@ box inverse_cdf_box(box cdf_box(double), double p)
 
     // 1. Make sure that cdf(low) < p < cdf(high)
     int interval_found = 0;
-    while ((!interval_found) && (low > -FLT_MAX / 4) && (high < FLT_MAX / 4)) {
+    while ((!interval_found) && (low > -DBL_MAX / 4) && (high < DBL_MAX / 4)) {
-        // ^ Using FLT_MIN and FLT_MAX is overkill
+        // for floats, use FLT_MAX instead
+        // Note that this approach is overkill
         // but it's also the *correct* thing to do.
         box cdf_low = cdf_box(low);
         if (cdf_low.empty) {