pyfcstm.render.expr

Expression rendering utilities for converting DSL AST nodes into language-specific text.

This module provides functionality to render expression nodes from the DSL abstract syntax tree into string representations for multiple language styles, including DSL, C, C++, Python, Java, JavaScript, TypeScript, Rust, and Go. Rendering is performed through Jinja2 templating with a small set of default templates and an optional extension mechanism to override or extend the template set.

The module exposes the following public functions:

Note

Templates must include a default key if you intend to render custom nodes that are not matched by the predefined entries.

Example:

>>> from pyfcstm.dsl import Integer
>>> from pyfcstm.render.expr import render_expr_node
>>> render_expr_node(Integer("42"), lang_style='python')
'42'
>>> render_expr_node(Integer("42"), lang_style='c')
'42'

fn_expr_render

pyfcstm.render.expr.fn_expr_render(node: float | int | dict | Expr | Any, templates: Dict[str, str], env: Environment) → str[source]

Render an expression node using the provided templates and Jinja2 environment.

This function detects the node type and selects the most specific template available. For operator nodes, it tries operator-specific templates such as UnaryOp(!) or BinaryOp(**) before falling back to the generic template. If the node is not a DSL expression, primitive Python types are converted into their corresponding DSL literal nodes. Any other object is rendered via repr().

Parameters:

  • node (Union[float, int, dict, dsl_nodes.Expr, Any]) – The expression node to render, which may be a DSL expression, a primitive value, or any Python object

  • templates (Dict[str, str]) – Dictionary mapping node types to Jinja2 template strings

  • env (jinja2.Environment) – Jinja2 environment for template rendering

Returns:

The rendered string representation of the expression node

Return type:

str

Raises:

KeyError – If no matching template is found and default is absent

Example:

>>> env = create_env()
>>> templates = _DSL_STYLE
>>> fn_expr_render(Integer(42).to_ast_node(), templates, env)
'42'
>>> fn_expr_render(True, templates, env)
'True'

create_expr_render_template

pyfcstm.render.expr.create_expr_render_template(lang_style: str = 'dsl', ext_configs: Dict[str, str] | None = None) → Dict[str, str][source]

Create a template dictionary for expression rendering based on the specified language style.

This function merges predefined templates for the requested language style with optional custom template entries. Custom entries override defaults with the same key.

Parameters:

  • lang_style (str) – The language style to use ('dsl', 'c', 'cpp', 'python', 'java', 'js', 'ts', 'rust', 'go')

  • ext_configs (Optional[Dict[str, str]]) – Optional additional template configurations to extend or override defaults

Returns:

A dictionary of templates for the specified language style

Return type:

Dict[str, str]

Raises:

KeyError – If lang_style is not recognized

Example:

>>> templates = create_expr_render_template('python', {'CustomNode': '{{ node.custom_value }}'})
>>> 'UFunc' in templates and 'CustomNode' in templates
True

render_expr_node

pyfcstm.render.expr.render_expr_node(expr: float | int | dict | Expr | Any, lang_style: str = 'dsl', ext_configs: Dict[str, str] | None = None, env: Environment | None = None) → str[source]

Render an expression node to a string representation in the specified language style.

This is a high-level convenience wrapper that prepares a Jinja2 environment, registers the expr_render filter and global function, and renders the provided expression node.

Parameters:

  • expr (Union[float, int, dict, dsl_nodes.Expr, Any]) – The expression to render

  • lang_style (str) – The language style to use ('dsl', 'c', 'cpp', 'python', 'java', 'js', 'ts', 'rust', 'go')

  • ext_configs (Optional[Dict[str, str]]) – Optional additional template configurations

  • env (Optional[jinja2.Environment]) – Optional pre-configured Jinja2 environment

Returns:

The rendered string representation of the expression

Return type:

str

Raises:

KeyError – If lang_style is not recognized

Example:

>>> from pyfcstm.dsl import Integer
>>> render_expr_node(Integer('42'), lang_style='python')
'42'
>>> render_expr_node(Integer('42'), lang_style='c')
'42'