A Collection of Code Snippets in as Many Programming Languages as Possible

This project is maintained by TheRenegadeCoder

Welcome to the Prime Number in Gnu Make page! Here, you'll find the source code for this program as well as a description of how the program works.

```
USAGE := Usage: please input a non-negative integer
# Numbers are represented as x's so that they can be manipulated with text functions.
# This idea is based on how the GNU Make Standard Library (https://github.com/jgrahamc/gmsl)
# handles numbers.
X0 :=
X1 := x
X2 := x x
X3 := x x x
X4 := x x x x
X5 := x x x x x
X6 := x x x x x x
X7 := x x x x x x x
X8 := x x x x x x x x
X9 := x x x x x x x x x
X10 := x x x x x x x x x x
# Constants
NUMBERS := 0 1 2 3 4 5 6 7 8 9
# Get rest of words in a list
# Arg 1: The list
# Return: List with first word removed
REST = $(wordlist 2,$(words $(1)),$(1))
# Repeatedly apply a function
# Arg 1: Name of function. This function must take two arguments:
# - Function Arg1: Current value
# - Function Arg2: New value
# Arg 2: The list to repeated apply the function to
# Arg 3: Initial value
_REDUCE = $(if $(4),$(call _REDUCE,$(1),$(call $(1),$(2),$(3)),$(firstword $(4)),$(call REST,$(4))),$(call $(1),$(2),$(3)))
REDUCE = $(call _REDUCE,$(1),$(3),$(firstword $(2)),$(call REST,$(2)))
# Split number into individual digits
# Arg 1: Number to split
# Return: Number split into individual digits
_SUBST_SPACE = $(subst $(2), $(2),$(1))
SPLIT_NUMBER = $(strip $(call REDUCE,_SUBST_SPACE,$(NUMBERS),$(1)))
# Indicate if valid number
# Arg 1: Number
# Return: $(X1) if valid number, $(X0) otherwise
IS_VALID_NUMBER = $(if $(strip $(1)),$(if $(filter-out $(NUMBERS),$(call SPLIT_NUMBER,$(1))),$(X0),$(X1)),$(X0))
# Add function
# Arg 1: Number 1 encoded as x's
# Arg 2: Number 2 encoded as x's
# Return: Number 1 + Number 2 encoded as x's
ADD = $(strip $(1) $(2))
# Multiply function
# Arg 1: Number 1 encoded as x's
# Arg 2: Number 2 encoded as x's
# Return: Number 1 * Number 2 encoded as x's
MULT = $(strip $(foreach _,$(2),$(1)))
# Multiply first number by 10 and add second number
# Arg 1: Number 1 encoded as x's
# Arg 2: Number 2
# Return: Number1 * 10 + Number 2 encoded as x's
MULT10_ADD_N = $(call ADD,$(call MULT,$(1),$(X10)),$(X$(2)))
# Represent number as list of x's
# Arg 1: Number
# Return: Number encoded as x's
CONVERT_NUMBER = $(strip $(call REDUCE,MULT10_ADD_N,$(call SPLIT_NUMBER,$(1)),$(X0)))
# Is divisible function
# Arg 1: Number encoded as x's
# Arg 2: Divisor encoded as x's
# Return: $(X1) if divisible, $(X0) otherwise
IS_DIVISIBLE = $(if $(strip $(subst $(2),,$(1))),$(X0),$(X1))
# Increment function
# Arg 1: Number encoded as x's
# Return: Number + 1 encoded as x's
INC = $(strip $(1) $(X1))
# Is less than function
# Arg 1: Number 1 encoded as x's
# Arg 2: Number 2 encoded as x's
# Return: $(X1) if Number 1 < Number 2, $(X0) otherwise
IS_LESS_THAN = $(if $(wordlist $(words $(call INC,$(1))),$(words $(2)),$(2)),$(X1),$(X0))
# Is less than or equal function
# Arg 1: Number 1 encoded as x's
# Arg 2: Number 2 encoded as x's
# Return: $(X1) if Number 1 <= Number 2, $(X0) otherwise
IS_LESS_OR_EQUAL = $(call IS_LESS_THAN,$(1),$(call INC,$(2)))
# Is prime function
#
# If number < 2, indicate composite
# Else if number < 3, indicate prime since number must be 2
# Else if number is even, indicate composite
# Else use trail division to determine if prime
#
# Arg 1: Number to check encoded as x's
# Return: $(X1) if prime, $(X0) if composite
IS_PRIME = $(strip \
$(if $(call IS_LESS_THAN,$(1),$(X2)),$(X0),\
$(if $(call IS_LESS_THAN,$(1),$(X3)),$(X1),\
$(if $(call IS_DIVISIBLE,$(1),$(X2)),$(X0),\
$(call TRIAL_DIVISION,$(1),$(X3))\
)\
)\
)\
)
# Determine if number is prime using trial division while divisor squared is
# less than or equal number, trying successive odd divisors
#
# Arg 1: Number to check encoded as x's
# Arg 2: Divisor (must be odd) encoded as x's
# Return: $(X1) if prime, $(X0) if composite
TRIAL_DIVISION = $(if $(call IS_LESS_OR_EQUAL,$(call MULT,$(2),$(2)),$(1)),\
$(if $(call IS_DIVISIBLE,$(1),$(2)),$(X0),\
$(call TRIAL_DIVISION,$(1),$(call ADD,$(2),$(X2)))),\
$(X1)\
)
# If invalid number, display usage statement
# Else if indicate if number is prime or composite
ifeq (,$(call IS_VALID_NUMBER,$(ARGV1)))
$(info $(USAGE))
else
NUMBER := $(call CONVERT_NUMBER,$(strip $(ARGV1)))
$(info $(if $(call IS_PRIME,$(NUMBER)),prime,composite))
endif
.PHONY:
all: ;@:
```

Prime Number in Gnu Make was written by:

- rzuckerm

If you see anything you'd like to change or update, please consider contributing.

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