Basics

puts

puts stands for put string, and outputs the text it is given

Filetype

The crystal filetype is .cr

crystal eval

eval executes the code that is passed to it. For example:

crystal eval 'puts "Hello, world!"'

will print out the line "Hello, world!"

crystal run

run builds and runs a source file, storing the built code in temporary storage

crystal build

build builds an executable that can be run without needing to compile every time. If you don't include the --no-debug flag, then build will also generate a .dwarf file that contains debugging information.

Building for release

By including the --release flag with the build command, the compiler optimises the code for execution speed, rather than compilation speed.

Running tests

To run a test file you use the command

crystal spec path/to/test/file.cr

Symbols

Symbols are essentially strings which are defined only once across the program, similar to constants. Symbols are defined like so:

:symbol

or for multi-word symbols:

:"multi word symbol"

You can get a string representation of a symbol by calling:

:symbol.to_s