allow models to also be executables

README.md

@@ -1,6 +1,6 @@
-# A minimalist calculator for fermi estimation
+# A calculator for distributions, for Fermi estimation
 
-This project is a minimalist, calculator-style DSL for fermi estimation. It can multiply, divide, add and substract scalars, lognormals and beta distributions.
+This project is a minimalist, calculator-style DSL for fermi estimation. It can multiply, divide, add and substract scalars, lognormals and beta distributions, and supports variables.
 
 ## Motivation
 
@@ -101,8 +101,31 @@ $ fermi -n 1_000_000
 
 - It's conceptually clearer to have all the multiplications first and then all the divisions
 - For things between 0 and 1, consider using a beta distribution
-- Because the model reads from standard input, you can pipe a model to it. For instance, try cat more/piano-tuners.f | fermi
+
-- You can also save a session to a logfile with tee. Try fermi | tee -a fermi.log
+
+### Integrations with linux utilities
+
+Because the model reads from standard input, you can pipe a model to it:
+
+```
+$ cat more/piano-tuners.f | fermi
+```
+
+You can also 
+
+...which means a model an executable file by adding the following at the top!
+
+```
+#!/bin/usr/fermi -f
+```
+
+
+You can save a session to a logfile with tee:
+
+```
+fermi | tee -a fermi.log
+
+```
 
 ## Different levels of complexity
 
@@ -143,10 +166,10 @@ Done:
 - [x] Allow input with K/M/T
 - [x] Document parenthesis syntax
 - [x] Specify number of samples as a command line option
+- [x] Figure out how to make models executable, by adding a #!/bin/bash-style command at the top?
 
 To (possibly) do:
 
-- [ ] Figure out how to make models executable, by adding a #!/bin/bash-style command at the top?
 - [ ] Add functions. Now easier to do with an explicit representation of the stakc
 - [ ] Think about how to draw a histogram from samples
 - [ ] Dump samples to file

fermi.go

@@ -411,10 +411,23 @@ replForLoop:
 
 func main() {
 	num_samples_flag := flag.Int("n", N_SAMPLES, "Specifies the number of samples to draw when using samples")
-	flag.Parse()
 	N_SAMPLES = *num_samples_flag
+	filename := flag.String("f", "", "Specifies a file with a model to run")
+	flag.Parse()
 
-	reader := bufio.NewReader(os.Stdin)
+	var reader *bufio.Reader = nil
+	if *filename != "" {
+		file, err := os.Open(*filename)
+		if err == nil {
+			reader = bufio.NewReader(file)
+		} else {
+			fmt.Printf("Error opening filename; reading from stdin instead\n")
+		}
+	}
+	if reader == nil {
+		reader = bufio.NewReader(os.Stdin)
+	}
 	stack := Stack{old_dist: INIT_DIST, vars: make(map[string]Dist)}
 	runRepl(stack, reader)
+
 }

more/executable-model.fermi

@@ -0,0 +1,10 @@
+#!/bin/fermi -f
+5M 12M     # number of people living in Chicago
+beta 1 200 # fraction of people that have a piano
+30 180     # minutes it takes to tune a piano, including travel time
+/ 48 52    # weeks a year that piano tuners work for
+/ 5 6      # days a week in which piano tuners work
+/ 6 8      # hours a day in which piano tuners work
+/ 60       # minutes to an hour
+=: piano_tuners
+exit