No Clocks

All R functions are technically closures (they all carry an enclosing environment), but the term earns its keep when a function captures variables from a parent that isn’t the global environment. Here is a counter that actually counts:

<<- is the only way to create mutable state in R’s functional world, because it searches parent environments for an existing binding and modifies it there. If it doesn’t find the variable in any parent, it creates one in the global environment. That is almost always a mistake.

R descends from the lambda calculus, by way of Scheme and a Bell Labs language called S. That ancestry shaped every part of the language. All of it traces back to a single design decision made in the 1970s.

Geospatial Data Preparation

Open options Open options can be specified in command-line tools using the syntax -oo <NAME>=<VALUE> or by providing the appropriate arguments to GDALOpenEx() (C) or gdal.OpenEx (Python). The following open options are supported: ENCODING=[<encoding_name>​/​""]: Override the encoding interpretation of the shapefile with any encoding supported by CPLRecode or to "" to avoid any recoding. DBF_DATE_LAST_UPDATE=YYYY-MM-DD: Modification date to write in DBF header with year-month-day format. If not specified, current date is used. ADJUST_TYPE=[YES​/​NO]: Defaults to NO. Set to YES to read the whole .dbf to adjust Real->Integer/Integer64 or Integer64->Integer field types when possible. This can be used when field widths are ambiguous and that by default OGR would select the larger data type. For example, a numeric column with 0 decimal figures and with width of 10/11 character may hold Integer or Integer64, and with width 19/20 may hold Integer64 or larger integer (hold as Real) ADJUST_GEOM_TYPE=[NO​/​FIRST_SHAPE​/​ALL_SHAPES]: Defaults to FIRST_SHAPE. Defines how layer geometry type is computed, in particular to distinguish shapefiles that have shapes with significant values in the M dimension from the ones where the M values are set to the nodata value. By default (FIRST_SHAPE), the driver will look at the first shape and if it has M values it will expose the layer as having a M dimension. By specifying ALL_SHAPES, the driver will iterate over features until a shape with a valid M value is found to decide the appropriate layer type. AUTO_REPACK=[YES​/​NO]: Defaults to YES. Whether the shapefile should be automatically repacked when needed, at dataset closing or at FlushCache()/SyncToDisk() time. DBF_EOF_CHAR=[YES​/​NO]: Defaults to YES. Whether the .DBF should be terminated by a 0x1A end-of-file character, as in the DBF spec and done by other software vendors. Previous GDAL versions did not write one.

gdal vector simplify simplifies geometries, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm. This done by the OGRGeometry::SimplifyPreserveTopology() method which preserves the topology per feature, but not for a whole layer. Thus gaps or overlaps between geometries that were initially contiguous may happen. To perform simplification that preserves shared boundaries between geometries, see gdal vector simplify-coverage. This command can also be used as a step of gdal vector pipeline.

GDALG output (on-the-fly / streamed dataset) This program supports serializing the command line as a JSON file using the GDALG output format. The resulting file can then be opened as a vector dataset using the GDALG: GDAL Streamed Algorithm driver, and apply the specified pipeline in a on-the-fly / streamed way.

Program-Specific Options --tolerance <TOLERANCE> The specified value of this option is the tolerance used to merge consecutive points of the output geometry using the OGRGeometry::SimplifyPreserveTopology() method The unit of the distance is in georeferenced units of the source layer.