Add acidity example

book/build.sh

@@ -34,6 +34,7 @@ generate_example musical_note_frequency "Musical note frequency" true
 generate_example body_mass_index "Body mass index" true
 generate_example pipe_flow_rate "Flow rate in a pipe" true
 generate_example recipe "Recipe" true
+generate_example acidity "Acidity" true
 generate_example xkcd_2585 "XKCD 2585" false
 
 generate_example numbat_syntax "Syntax overview" false

book/src/SUMMARY.md

@@ -13,6 +13,7 @@
     - [Body mass index](./example-body_mass_index.md)
     - [Flow rate in a pipe](./example-pipe_flow_rate.md)
     - [Recipe](./example-recipe.md)
+    - [Acidity](./example-acidity.md)
     - [XKCD 2585](./example-xkcd_2585.md)
 
 # Numbat language reference

book/src/example-acidity.md

@@ -0,0 +1,13 @@
+<!-- This file is autogenerated! Do not modify it -->
+
+# Acidity
+
+``` numbat
+# Compute the pH (acidity) of a solution based
+# on the activity of hydrogen ions
+
+fn pH_acidity(activity_hplus: Concentration) -> Scalar =
+    - log10(activity_hplus / (mol / L))
+
+print(pH_acidity(5e-6 mol / L))
+```

book/src/example-numbat_syntax.md

@@ -60,9 +60,9 @@ let y3: Length / Time = 2 m/s      # more complex type annotation
 
 # 5. Function definitions
 
-fn foo(x: Scalar) -> Scalar = 2 * x + 3         # A simple function
-fn speed(s: Length, t: Time) -> Speed = s / t   # Two parameters
-fn my_sqrt<T>(x: T^2) -> T = x^(1/2)            # A generic function
+fn foo(z: Scalar) -> Scalar = 2 * z + 3                 # A simple function
+fn speed(len: Length, dur: Time) -> Speed = len / dur   # Two parameters
+fn my_sqrt<T>(q: T^2) -> T = q^(1/2)                    # A generic function
 
 # 6. Dimension definitions
 

examples/acidity.nbt

@@ -0,0 +1,10 @@
+# Compute the pH (acidity) of a solution based
+# on the activity of hydrogen ions
+#
+# https://en.wikipedia.org/wiki/PH
+
+fn pH_acidity(activity_hplus: Concentration) -> Scalar =
+    - log10(activity_hplus / (mol / L))
+
+print(pH_acidity(5e-6 mol / L))
+assert_eq(pH_acidity(5e-6 mol / L), 5.3, 0.1)